The Dow rose 1.55 percent, while the S&P 500 was up 1.14 percent. All 10 major S&P sectors were higher, led by a 2.9-percent rise in the energy sector .SPNY. Crude prices settled up 3.7 percent on hopes that OPEC and non-OPEC producers would tackle an unrelenting supply glut. [O/R]

Investors have been reeling from a turbulent start to the year that has left the S&P down 7 percent from the end of 2015.

"This is a schizophrenic market. Big up days, big down days. No real direction," said Tim Ghriskey, chief investment officer of Solaris Group in Bedford Hills, New York.

That left the gap between U.S. and Chinese stock indexes at its widest since at least August.

Shares of Apple (AAPL.O), which is scheduled to report results after the close, were up 0.6 percent. The iPhone maker's comments on its China business will be in focus because of wide concerns about a potential slowdown in demand.

At 2:48 pm, the Dow Jones industrial average .DJI was up 245.95 points to 16,131.17 and the S&P 500 .SPX gained 21.43 points to 1,898.51.

While the U.S. Federal Reserve is not expected to move on interest rates at its two-day meeting, which began on Tuesday, investors will parse the Fed's commentary to gauge how recent global turmoil affects the central bank's outlook.